A multiple-choice test has 20 questions. There are four choices for each question. A student comes to class with four different colored balls of identical shape and size in her pocket. She has decided to draw one ball from her pocket per question and allow the color of the ball to select the answer for each question. What type of probability distribution can be used to figure out her chance of getting 10 questions right?
A. Hypergeometric
B. Poisson
C. Normal
D. Binomial
Which of the following cannot generate a Poisson distribution?
A. The number of people at a movie theatre on Friday evening
B. The number of customers arriving at an automatic teller machine (ATM) in a minute
C. The number of defects in a new automobile
D. The number of goals in the World Cup soccer game
Which of the following is a characteristic of every binomial distribution?
A. Each outcome is dependent on the previous outcome.
B. The probability of success increases from trial to trial.
C. Each outcome is mutually exclusive.
D. The outcome of the trial depends on the number of trials.
The average qualifying speed for a championship NASCAR® race is 145.65 mph and the standard deviation is 9.45 mph. Only drivers who obtain z-scores greater than 1.2 will qualify for the race. If the speeds are normally distributed, what minimum speed must be clocked to compete for the trophy?
A. 146.9 mph
B. 155.2 mph
C. 157.0 mph
D. 174.8 mph
Trudy Jones recently completed her certification examination and learned that her z-score was -2.5. The examining board also informed her that a failure to pass would equal all scores that were one or more standard deviations below the mean and that those with scores higher than two standard deviations above the mean would receive a special commendation award. Trudy can conclude that she
A. failed the exam
B. needs more data to determine if she passed the exam
C. passed the exam and will receive a special commendation award
D. passed the exam, but no commendation award is forthcoming
The use of the student’s distribution requires which of the following assumptions?
A. The sample size is greater than 30.
B. The population variance is known.
C. The population is normal.
D. The sample is drawn from a positively skewed distribution.
The standard error of the sample mean is equal to 5 when n=25. If the sample size increases by a factor of four, how will the standard error change?
A. It will be double.
B. It will be cut in half.
C. It will be cut to 1/4 of 5.
D. It will quadruple.
For a sample size of 1, the sampling distribution of the mean will be normally distributed
A. regardless of the shape of the population
B. only if the shape of the population is positively skewed
C. only if the population values are larger than 30
D. only if the population is normally distributed
A 95% confidence interval for the population mean indicates that
A. with an infinite number of samples, there’s a 5% chance that the population mean will be outside the interval
B. more sampling is required to increase the confidence interval to 100%
C. the sampling process is biased
D. 95% of the observations from any sample will fall within the interval
A random sample of 16 ATM transactions at the First National Bank of Flintrock revealed a mean transaction time of 2.8 minutes with a standard deviation of 1.2 minutes. The width, in minutes, of the 95% confidence interval for the true mean transaction time is
A. ± 0.639
B. ± 0.588
C. ± 0.300
D. ± 2.131
All other things being equal, which is narrower, a 95% confidence interval with n=100 or a 99% confidence interval with n=30?
A. The 95% confidence interval
B. The 99% confidence interval
C. The same width
D. Need the margin of error to tell
When the only sources of variation in a production process are caused by chance, the process is said to be
A. out of balance but under control
B. out of control but in balance
C. under control
D. out of control